Keywords:silicon crystal, nitrogen-point defect complex, infrared absorption
Nitrogen in silicon usually forms interstitial pair (NiNi) and its concentration is measured by the infrared absorption (IR) by the pair complexes (NNOn, n = 0-2). Also it is known that N in CZ silicon at low concentrations forms shallow thermal donor (STD) of NO pair complexes (NOn, n = 1-4). We found the infrared absorption for the local vibration modes (LVM) of STD and identified the origin. It was supported by the calculation. Furthermore, we found that the absorption line at 551 cm-1 decreased after the electron-beam irradiation and the 688 cm-1 line appeared by the post annealing at 400 oC in FZ silicon, and assigned the latter as VVNN which was predicted theoretically. We assigned 551 cm-1 absorption as Ni and found 689cm-1 in as-grown FZ crystal and assigned as VNs. Here we examined STD further. We add (ONO)On to construct 7 structures. Multiple absorption peaks were reported.